The proposed research is designed to provide information concerning the coupling of energy metabolism to substrate translocation by the general amino acid transport system of Saccharomyces cerevisiae, to characterize the individual components of the transport system at a molecular level, and to determine the mechanism of regulation which controls the expression of transport activity. To accomplish these goals we propose to: (1) Determine the role of proton gradients and membrane potentials in the energetics of amino acid transport; (2) Identify, isolate, purify and characterize the energy coupling factors which function in amino acid transport; (3) Isolate, purify and characterize transport related binding proteins; (4) Characterize the regulatory factors which modulate transport activity using biochemical and genetic methodology.